Theoretical electronic structure with rovibrational and dipole moment calculation of the SiS Molecule

Abstract

The quantitative distribution of the molecular abundances in the universe is a classical problem in astronomy, astrophysics and cosmo-chemistry. Astrophysicists are interested in determining the abundances of molecular species in order to: (1) Know the primordial composition of the solar system, and its relation to the past and present composition of the earth. (2) Have a complete understanding of physical and chemical processes taking place in the stellar atmospheres and the interstellar medium (3) Test the hypotheses that have been proposed for element formation. To investigate the presence of astronomical sources, experimental astrophysicists usually study the wavelength and intensity of light that they emit. Many diatomic molecular species are present in various astrophysical sources, however, the theoretical studies on such species are not enough and information is missing in that area. Knowledge of the electronic structure, Franck-Condon factors (FCFs), and other related quantities for a band system of a diatomic molecule is essential to arrive at its astrophysically significant parameters such as kinetics of the energy transfer, radiative lifetimes, band intensity, vibrational temperature, etc. In this view, the spectroscopic and ro-vibrational constants, FCFs of several electronic states of the diatomic molecule SiS electronic have been evaluated in this work. We performed theoretical calculation of the low-lying electronic state, of the molecule SiS by using the Complete Active Space Self Consistent Field (CASSCF) method followed by the Multi Reference Configuration Interaction with Davidson correction MRCI+Q. The potential energy along with the dipole moment curves of these states have been calculated along with the spectroscopic constants Re, ωe, Be, and Te. Additionally, the Rotation-vibration lines for the considered electronic states were obtained by direct solution of the nuclear motion Schrödinger equation using the canonical approach with program Rovib-1